The guiding of aircraft, for example airliners, when they reach their parking area, usually in the immediate vicinity of an embarkation and disembarkation bridge, is relatively complex.
This guiding has been for a long time carried out by an operator, called a "batman" who is provided with two signals, one in each hand, and gives to the pilot, by conventional gestures, the instructions enabling him to bring the aircraft to a position in which the door is located in front of the disembarkation bridge. This is arduous work in a noisy and dangerous environment.
For the purpose of providing a solution to this problem, there have already been employed magnetic detecting means placed in the ground of the parking area and permitting the detection of the aircraft and the translation of its position on a display panel visible from the aircraft to enable the pilot to position the aircraft correctly. A device of this type is disclosed, for example, in the patent GB-A-1,508,418. Such a device is very costly to set up and in practice only permits guiding the aircraft in a small area.
Furthermore, this magnetic detecting device is placed in a complex hertzian and electromagnetic environment and does not operate under the best conditions.
Another proposed solution comprises using a device sold under the trademark UCRAFT and comprising a mast carrying an articulated arm at the end of which is provided a luminous bar which, in accordance with instructions previously entered as a function of the type of the aircraft, is placed in space at a point which is a function of the type of the aircraft and corresponds to the front of the pilot's cabin so that, when the pilot sees this point, he steers the aircraft and stops over the point.
Such a device needs a considerable mechanical infrastructure and, being composed of moving parts, requires a costly supervision and maintenance.
Guiding devices of the optical type have also been proposed for aircraft which comprise, provided on the fuselage of the aircraft, reference marks or codes, which may be detected by optical means for the purpose of locating the position of the aircraft. Such devices are disclosed in U.S. Pat. Nos. 3,775,741 and 4,249,159. These devices require marks or modifications on the fuselage of the aircraft, which is excluded in practice. Furthermore, no indication is furnished concerning the distance of the aircraft from a reference location.
In U.S. Pat. No. 3,729,262, there is provided a visual aircraft guiding device based on the use of high-intensity lamps or light sources and Fresnel lenses so as to generate two bars of light which are seen by the pilot of the aircraft and vary in their respective reference in accordance with the displacement of the aircraft. This device does not permit measuring the distance between the aircraft and a reference and requires complex optical adjustments without providing high precision.
U.S. Pat. No. 4,736,247 discloses a distance measuring device employing laser means whose beam is directed by an array of mirrors and divided into two secondary beams through a prism, the first secondary beam being directed at a video camera for creating a reference for the measurement, and the second secondary beam after having travelled through an optical path passing through three mirrors, is sent onto the moving body whose distance to the reference point is desired to be known. The two end mirrors are oriented by motors which return angular data to the computer. This device is adapted to measure the distance between two moving bodies, such as satellites. It must generate its own reference and requires an extremely costly and very complex technology.
U.S. Pat. No. 4,760,269 discloses a device for measuring the distance to an object in which a very precise image is projected by laser means onto a planar surface of the object and the image received by a video camera is studied. This device requires, on one hand, the production of an extremely precise image, and, on the other hand, the presence on the object of a planar surface onto which the image is projected, these two requirements being incompatible with the application to the guiding of an aircraft towards its parking position.
U.S. Pat. application No. EP-A-0,145,957 discloses a light emitting unit which emits a fine lasar beam and comprises a video camera for generating a measurement of the distance by triangulation of a surface relative to a known reference, a shape analysis moreover permitting overcoming the problem of non-orthogonality of this surface relative to the viewing axis of the camera. This device is intended for measurements of short distance on object surfaces which may be located in a very small zone and in a well-defined environment, such as machine tools. This device could not be adopted for use in the guiding of aircraft toward the parking position.